Hundreds of small earthquakes at Yellowstone National Park in recent weeks have been an unsettling reminder for some people that underneath the park's famous geysers and majestic scenery lurks one of the world's biggest volcanoes.

Scientists working towards pancreatic cell transplants as a cure for diabetes have taken the first step to getting around the problem of immune rejection. Transplanted genetically engineered cells in mice lasted a few months before being rejected.